1. Field of the Invention
This invention relates to work platforms used with cranes and telescopic boom assemblies, particularly to a universal self-contained work platform attachment with auto-powered leveling and rotation for mobile and boom truck cranes, wherein when such mobile and boom truck cranes include a swing-jib mounting system, the invention can be mounted to the standard crane tip swing-jib mounting plates already incorporated therein, advantageously using the existing pinning holes and pins provided by the swing-jib boom system's manufacturer. It is also contemplated for the present invention to be used with telescopic boom assemblies, and it becomes securely mounted thereto using only the previously mentioned mounting plates, and does not require any additional bolting, welding, or attachment of any other fixtures where the telescopic boom assembly incorporates a swing-jib attachment system. The auto-powered leveling and rotation capability of the present invention, among its other features and advantages, can instantly transform any crane with a swing-jib attachment system into a modern day state-of-the-art aerial lift, which has not been done before. Another advantage of the present invention is that its size and load capacity can be made greater than most prior art man baskets used with mobile and boom truck cranes, providing a greatly increased work area envelope with more side reach and greater height. The onboard powered-leveling system of the present invention work platform attachment maintains the platform in a level orientation, as the attached crane boom is articulated up or down, regardless of the location of its load's center of gravity relative to the platform, including cantilevered and off-set loads. The present invention also incorporates a rotation mechanism that allows 180-degree platform rotation when fully-loaded, with the option of stable/balanced vertical articulation leveling and platform rotation at the same time. Further advantages of the present invention include, but are not limited to, a redundant ground-operated radio remote control system having the same functions as the control box on the platform, platform positioning above the boom and boom tip that allows unrestricted work access above and around the boom tip, and legal road travel, as when the crane boom to which a present invention platform is attached is stowed over the chassis cab, the platform's very compact and low profile design is able to fit within the permitted legal-road-travel envelope while it is secured to the boom tip swing-jib mounting plates (also referred to elsewhere herein as ‘swing-jib brackets’). In addition, since the present invention is a self-contained and fully functioning platform, it could also be attached to cranes and telescopic boom assemblies without a swing-jib attachment system, however, crane modification (bolting, welding, and/or other) is typically required to provide a secure work platform attachment point.
2. Description of the Related Art
The mobile crane boom industry has advanced many new crane designs and other product technology over the last 15 years by adding new features and design improvements, such as stronger materials, onboard load-monitoring computers, optional radio remote controls that allow operation of all crane functions from the work platform, load-sensing computerized hydraulic systems, and much more. The one area that has not advanced is work platforms, and those in use today are basically the same as 40 years ago. A description of what historically has been, and still is, standard for the crane industry regarding removable or pin-on work platforms follows below. Some disadvantages of this prior art are also mentioned below, along with information relating to dedicated work platforms having structure specific to a particular manufacturer or model.
The standard crane work platform in use today incorporates a pendulum-style gravity-leveling system wherein the platform hangs from, or pivots on, a shaft, with three designs or types of such platform attachments currently used with boom truck cranes. All three of these types of prior art platforms have restricted work access above and around the boom tip (in contrast to the present invention which has unrestricted overhead access). One prior art pendulum-style gravity-leveling platform is attached to a pivot pin on the side of crane boom, another has an attachment pivot pin inside the center of its platform and a rotation mechanism, and the third has its platform mounted to the end of the crane boom using a two-pin yoke-style hanging attachment. The platform mounted to the side of crane tip is limited in useable work range because the boom blocks much of the overhead work area, as well as work on the side of the platform attached to the crane. Also, while the prior art work platform with the centered pivot pin and rotation mechanism on the crane boom advantageously has 360-degree rotation, its pivot attached inside the basket takes up valuable platform payload space. Similarly, the generally U-shaped exterior support structure portion of the yoke-style platform's boom tip attachment design often obstructs the work access range of onboard personnel. While this center-mounted rotating/pivoting prior art platform on a crane boom advantageously has 360-degree rotation, its pivot is attached inside the basket, which takes up valuable platform payload space and also blocks overhead work access range. Furthermore, when cranes have their booms stowed over the chassis cab, a yoke-style platform attached to would hang too far below the boom for road-legal-travel, obstructing at least part of the driver's view of the road ahead. In contrast, the present invention platform has its platform-leveling pivot hinge pin located near its floor, which reduces its overall height and makes it much shorter and compact than a pendulum/gravity leveled platform. This enables road-legal travel for the present invention because its compact design allows it to be stowed less than the road-legal height limit of 13-feet and 6-inches, and also allows its bottom surface to clear the chassis cab roof, while the present invention's rotation capability allows its platform to be positioned outboard and parallel to the side of a crane boom, where it clears both the cab chassis roof and driver's vision.
Also important is that pendulum-style gravity-leveling platform designs have an inherent negative flaw that causes them to swing and rock if payload and people inside the platform move while the supporting crane is raised or lowered. In addition, when the prior art platform's brake is applied to lock the leveling, and any the onboard personnel of payload load in the platform subsequently moves to a new location, the center of gravity of the platform is also likely to change Thus, unless the personnel and/or other load are moved back to their original positions before the brake is released to re-establish the original center of gravity, or other provisions are taken to rebalance payload and/or personnel, upon brake release the platform will suddenly tilt out-of-level and chaotically throw the payload and personnel into the side rails of the platform, causing distress and damage. The same situation occurs when the brake is engaged and the platform is rotated. Should the center of gravity after rotation become significantly changed, when the brake is released the platform will swing violently. Even the pendulum platforms having a mechanical hand-rotation must have personnel and payload centered to maintain a level orientation and avoid violent swinging. Thus, historically during routine crane movement, a work platform's center of gravity had to be kept in line with its pendulum plumb line, with care taken at the outset to remember the initial balance and positioning of onboard personnel and loads, as well as care taken to rebalance onboard personnel and loads before the platform is rotated out of its locked position, otherwise it will be out-of-level with unpleasant and potentially dangerous consequences. In contrast, the present invention platform has auto-powered leveling that instantly compensates for any changes in the platform's center of gravity due to repositioning movement of payload and/or personnel, and does not allow chaotic movement to occur at elevation upon brake release.
The present invention platform is also distinguishable from the manufacturer-dedicated platforms currently in use with mobile crane booms. Mobile crane boom manufacturers do not currently offer, nor are mobile crane booms designed for, a factory-ready (or an after-market) self-contained work platform that employs, adapts, and/or otherwise incorporates modern aerial lift features with self-platform leveling and rotation, and any attempt to do so by means other than the self-contained and self-powered work platform attachment herein would require modification to the entire mobile crane boom assembly to supply the associated platform with power (hydraulic or electric) for its needed platform leveling and rotational features, and would also require a new mechanically-designed platform mounting structure and assembly. Furthermore, for well over twenty years, many aerial lift boom trucks have had work platforms or baskets that allow them to function as cranes. While these work platforms and baskets have many features and mechanisms that are similar to those of the instant invention, such as powered mechanical leveling or platform rotation, these work platforms are also designed and manufactured with many dedicated/integral components that work only with their own specifically designed product, and cannot be easily adapted for other use. In addition, the platform mounting bracket typically used to secure a dedicated work platform to a main crane boom has a vertical height similar to that of the work platform, with the connection thereto involving a substantial portion of one side of the platform. In contrast, the connecting/support member used between the present invention work platform attachment and swing-jib sheave head mounting plates is (in comparison) a substantially planar platform mounting structure that is advantageously connected to the base/bottom surface of the work platform attachment, making the present invention structure different and distinguishable from known manufacturer-dedicated work platforms. Furthermore, such platforms are not self-contained, and power from the associated truck is needed for its work platform leveling and rotation functions. Thus, such prior art platforms are not designed to function as an after-market add-on work platform attachment, as is the present invention, instead being an original and dedicated integral component of its associated aerial lift boom truck. In addition, these aerial lift boom trucks do not have a swing-jib or a boom tip designed sheave head configured for a swing-jib, and thus do not secure their platforms in position using a standard swing-jib pinning system. Instead, they are all designed to have a platform or basket attach to the outer boom tip by means of welded or bolted attachment points specifically designed for support of their individual platforms. Furthermore, in prior art and current aerial lift boom trucks, hydraulic or electrical power for platform leveling and rotation is typically supplied from the ground by the supporting vehicle, an auxiliary engine, or a large battery-powered power unit, via hose/cable carriers or retractable reels attached to the boom assemblies, none of which are required during use of the self-contained self-powered present invention embodiments.
Thus, in contrast to the prior art, the present invention comprises the following features and advantages which make it structurally distinguishable. Leveling of the present invention platform is accomplished by means of an onboard mechanically-powered automatic hydraulic/electronic leveling system that senses when the platform is in an out-of-level state, and then operates a hydraulic leveling cylinder to articulate the platform level while the crane boom is raised or lowered, regardless of the position of the platform, onboard personnel, or its payload. When the crane boom is stopped, the platform's leveling cylinder employs several holding valves that lock the platform into a level orientation. Thus, a loaded present invention platform can be safely rotated in the horizontal plane while it is in the locked position, and its load, including personnel, are also safe as a result of its powered-leveling while the boom is being raised or lowered. Also, in addition to powered-leveling, user-friendly and safer platform rotation will now be available on mobile cranes due to other integral design features of the present invention, including its strong rotational bearing and drive mechanism, a torsion-resistant tubular platform mount, and a rigid and strong structural mounting bracket that anchors the present invention platform to the strong structural swing-jib sheave head while transferring all torsion and bending moments induced by off-set platform loads to the swing-jib sheave head.
In contrast to the present invention, the only prior art form of rotation for mobile crane platform boom attached platforms currently available involves a cumbersome and antiquated design consisting of gravity leveling, and the use of a manual level-locking brake or cylinder, wherein those aboard the platform are required to rebalance its onboard personnel and payload as close as possible to original positioning, before brake/lock release to avoid experiencing chaotic platform movement should the platform's center-of-gravity change while at elevation. In addition, platform rotation in a prior art gravity-leveled platform is typically performed by an onboard operator manually hand-cranking a gear box rotation mechanism, positioned above the platform. This prior art design is dangerous, expensive to purchase, and not user-friendly. In contrast, the present invention platform advantageously incorporates a hydraulic-powered rotation drive gear assembly that can rotate it a total of 180-degrees, with the present invention platform being maintained in a level state during all rotation (0-to-180-degrees) and as the crane boom is raised or lowered. Furthermore, the total power supply, mechanical actuation, and function controls in the self-contained present invention are all encompassed in a self-contained 12-volt battery-powered power pack integral with its platform assembly, thus eliminating the need for connecting hoses or power cables alongside the booms or platform, as well as the need for hose reels or cable carriers, unless application dictates otherwise. In addition, a shear ball bearing and hydraulic gear drive mechanism in the present invention allows a very large 10-foot long cantilevered work platform to be mounted in an offset position relative to the crane boom, platform hinge pivot pin, or center of platform rotation, yet continuously maintained in a level orientation in all positions of rotation (0-to-180-degrees), even when its is fully loaded to its 1,000 pound capacity and rotated. The universal-style mounting design of the present invention also allows it to be mounted to most commercial crane boom ends having a swing-jib mounting system, as it is configured to use the swing-jib anchor points that most cranes now incorporate as a standard feature. The swing-jib mounting system allows for a simple 4-pin connection of the present invention platform to a crane boom end. In addition, the mechanically-powered leveling feature of the present invention allows for road-ready stowed travel on a crane's boom tip. Since it does not rely on a pendulum/gravity leveling system and its platform-leveling pivot hinge pin can be located near its floor, its overall height is reduced, making it much shorter and compact than a pendulum/gravity leveled platform, which enables standard boom truck cranes with the present invention attached to it to fit and travel within a road legal travel envelope on roads and highways. Present invention design also enables a 10-foot long platform to be rotated outboard and parallel to the side of a boom within road legal width requirements, while concurrently clearing the cab chassis roof and driver's vision, thus allowing large and small present invention platforms alike to be left on the crane boom end during road travel. In contrast, the current designs of prior art side-mounted and yoke-mounted crane work platforms instead typically have a long pendulum design with a low center-of-gravity configured to reduce the chaotic rocking motion during platform elevation change that can lead to injury/damage of personnel and payload. Thus, when stowed over a chassis cab, they are usually not compact, which prevents road-legal-travel in a mounted and ready-to-use position. While a shorter pendulum length would allow a shorter overall stowed height and the possibility of road-legal-travel, onboard personnel using such a platform would have the nearly impossible task of re-establishing a balanced position/location for people and payload before each brake release in advance of a platform elevation change, and if the needed balance is not substantially achieved, chaotic platform rocking would ensue.
After a review of patents on the U.S. Patent Office website using International Classifications 182/2.4, 182/2.9, 212/168, 212/300, and 340/685, the inventions thought to be the closest in structure to the present invention are those disclosed in U.S. Pat. No. 4,553,632, to Griffiths (1985), U.S. Pat. No. 7,926,670 to Schneider (2011), U.S. Pat. No. 4,537,281 to Endres et al. (1985), U.S. Pat. No. 4,653,654 to McDaniel, Jr. et al. (1987), U.S. Pat. No. 6,036,035 to Asano et al. (2000), and U.S. Pat. No. 4,799,573 to Simnovec et al. (1989). The Griffiths patent discloses an automatic leveling device for crane-boom-supported work baskets that senses and adjusts leveling via plumb sensors and potentiometers. The Griffiths invention also includes a battery that supplies power to an electronic leveling sensor, a servo valve, and an actuator for occasions when the basket needs to be electrically isolated from the ground. In 1983, when the Griffiths patent application was filed, others were making and using electronic leveling sensors on work baskets/platforms, such as those available from P-Q Controls in Bristol, Conn., but these baskets/platforms did not have onboard battery power. Also, after reading about the Griffiths, it is concluded that its basket is an integrally designed and incorporated part of its associated boom crane, as the Griffiths disclosure does not include any supportive layout instructions or design plans that would enable its basket to be an after-market work platform attachment. The Schneider invention discloses a gravity-leveling work platform that can be attached to the tip of a swing-jib crane boom and stowed for road-legal highway travel, however, the Schneider invention does not teach a work platform with the many features and advantages provided by the also stowable and road-legal present invention platform attachment. The Endres invention is a yoke-mounted platform having a gravity/pendulum leveling design and a brake that locks the leveled platform in-place when the boom is stopped, so that people can safely move around inside the platform without a risk of placing the platform in an out-of-level orientation. The Endres platform also incorporates a shock absorber that slows rotation of its arms 82 and 84 around pivot pins 94/96, which that could occur as a result of unbalancing movement by onboard personnel or payload before its lock/brake is released. After the 1985 Endres invention, newer art has similarly used a hydraulic cylinder with a fluid loop path from its extend side port to its retract side port (a plumbed-in line between the two ports being some sort of on/off hand-valve that stops fluid travel), which stops travel of the cylinder shaft and locks the platform against further movement. Although the shock absorber of the Endres invention is important for those moving around inside its work platform (to prevent them from tipping out when any unbalanced movement occurs), but a shock absorber feature is unnecessary in the present invention as a result of its onboard powered-leveling system. The McDaniels invention is a side-mounted gravity-leveled work platform that uses the swing-jib sheave head pinning point to attach itself to a crane boom. The side-mounted gravity-leveling system uses the same type of art employed in the Endres yoke-mounted platform system for leveling and locking its platform, which is distinguishable from the non-gravity-leveled present invention. The Simnovec invention is a self-leveling work platform with an overhead connection to a crane boom, and appears to be designed for a knuckle boom or an aerial lift boom. In contrast to the present invention, the Simnovec platform requires boom modification prior to its attachment. No other work platform attachment for mobile and boom truck cranes is known with the same structure or function, or to provide all of the features and advantages of the present invention.